When laboratory analyses are being carried out it is known that it is often necessary to provide a predetermined amount of a liquid substance, such as a reagent, in a small vessel. To achieve this a graduated pipette is generally used with the aid of which a certain amount of the reagent is drawn off by suction and a portion of the amount taken is allowed to flow by gravity into the vessel, the volume and the amount of the reagent dispensed in this way being determined by the level difference which is read from the graduation of the pipette.
When, however, the amount of reagent is very small this method has the disadvantage of lacking in accuracy.
More precisely, as a result of the capillarity phenomenon in the calibrated tube, the amount which is dispensed into the vessel can only be determined with a degree of accuracy which corresponds to the volume of one drop, and this volume is not negligible with respect to the volume of the measured amount.
Moreover, the method described above is time-consuming, requires a certain amount of skill and does not readily lend itself to being used in an automatic line. It is consequently of little practical use when a large number of measured amounts have to be prepared.
Preferred embodiments of the present invention overcome these disadvantages and provide an accurate process for dispensing a very small measured amount of a liquid substance into a vessel, this process being able to be readily applied to an automatic filling device. The present invention can naturally be used also for measuring out somewhat larger quantities.